Lightning protection in aircrafts constructed with carbon fiber reinforced plastic

ABSTRACT

The embodiments described herein provide for lightning protection in aircrafts constructed with Carbon Fiber Reinforced Plastic (CFRP). In one embodiment, the apparatus includes a first Carbon Fiber Reinforced Plastic (CFRP) panel, a second CFRP panel that overlaps with the first CFRP panel in a vertical direction, and a fastener to join the first CFRP panel with the second CFRP panel, the fastener extending in the vertical direction in an area where the first CFRP panel and the second CFRP panel overlap. The apparatus further includes a plurality of electrically conductive pins in each of the first CFRP panel and the second CFRP panel, wherein the pins extend in the vertical direction proximate to the fastener to electrically connect the first CFRP panel and the second CFRP panel in the area where the first CFRP panel and the second CFRP panel overlap.

RELATED APPLICATIONS

This document is a continuation of U.S. Pat. No. 11,292,611, issued onApr. 5, 2022, which is a continuation of U.S. Pat. No. 10,875,663,issued on Dec. 29, 2020, both of which are hereby incorporated byreference.

FIELD

This disclosure relates to the field of aircrafts, and in particular, tolightning protection in aircrafts constructed with carbon fiberreinforced plastic.

BACKGROUND

Modern aircrafts are increasingly constructed with components made ofCarbon Fiber Reinforced Plastic (CFRP). Compared with aluminum alloysconventionally used in aircraft and aerospace construction, CFRPprovides a structure that is strong and lightweight. However, since CFRPpanels have low conductivity, high levels of current from a lightningstrike may be undesirably concentrated where two panels are joinedtogether by a metal fastener.

SUMMARY

Conductive pins are inserted through a CFRP panel to increasethrough-thickness conductivity near a fastener. In the event of alightning strike, the pins distribute the current more evenly in thecomposite layers of the CFRP panel and spread through-thickness currentconduction away from the fastener. The pins are therefore able todecrease the probability of ignition hazards, particularly in areas ofan aircraft such as the wings where fuel sources may be present. Unlikeconventional lightning mitigation techniques (e.g., covering thefastener with a polysulfide cap seal, applying edge sealant, and/orbonding existing panels with a conductive splice), the pins may befabricated within a CFRP panel to reduce weight and may be inserted inan automatable fashion with no additional cure time to benefit factoryflow.

One embodiment comprises an apparatus that includes a first Carbon FiberReinforced Plastic (CFRP) panel, a second CFRP panel that overlaps withthe first CFRP panel in a vertical direction, and a fastener to join thefirst CFRP panel with the second CFRP panel, the fastener extending inthe vertical direction in an area where the first CFRP panel and thesecond CFRP panel overlap. The apparatus further includes a plurality ofelectrically conductive pins in each of the first CFRP panel and thesecond CFRP panel, wherein the pins extend in the vertical directionproximate to the fastener to electrically connect the first CFRP paneland the second CFRP panel in the area where the first CFRP panel and thesecond CFRP panel overlap.

Another embodiment comprises a method that includes identifying a firstCarbon Fiber Reinforced Plastic (CFRP) panel and a second CFRP panel tobe joined, determining an area where the first CFRP panel and the secondCFRP panel are to overlap in a vertical direction, and determining alocation for a fastener to be inserted into the area in the verticaldirection to join the first CFRP panel and the second CFRP panel. Themethod further includes inserting a plurality of electrically conductivepins into the area in the vertical direction at positions proximate tothe location for the fastener.

Another embodiment comprises a composite structure for an aircraft. Thecomposite structure includes a plurality of Carbon Fiber ReinforcedPlastic (CFRP) panels that are horizontally adjacent with one another,each CFRP panel including: an upper surface having a mesh foil, afastener inserted through the CFRP panel in a vertical direction, thefastener configured to secure the CFRP panel to a metallic frame of theaircraft located proximate to a lower surface of the CFRP panel, and aplurality of electrically conductive pins extending in the verticaldirection to electrically connect the mesh foil and the metallic frameof the aircraft.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments or may be combined in yetother embodiments, further details of which can be seen with referenceto the following description and drawings.

DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are now described, by way ofexample only, with reference to the accompanying drawings. The samereference number represents the same element or the same type of elementon all drawings.

FIG. 1 illustrates an aircraft in an example embodiment.

FIG. 2 illustrates a wing of the aircraft that includes a compositestructure of multiple panels in an example embodiment.

FIG. 3 is a partially exploded view of CFRP panels joined together by afastener in an example embodiment.

FIG. 4 illustrates a partially exploded view of CFRP panels joinedtogether by a fastener and enhanced with electrically conductive pins inan example embodiment.

FIG. 5 is a side view of the CFRP panels joined together by a fastenerand enhanced with electrically conductive pins in an example embodiment.

FIG. 6 is a side view of the CFRP panels enhanced with electricallyconductive pins in another example embodiment

FIG. 7 is a side view of the CFRP panels enhanced with electricallyconductive pins in yet another example embodiment.

FIG. 8 is a side view of an adjacent CFRP panel connected withelectrically conductive pins in an example embodiment.

FIG. 9 is a side view of adjacent CFRP panels connected withelectrically conductive pins in another example embodiment.

FIG. 10 is a block diagram of a composite manufacturing environment inan example embodiment.

FIG. 11 is a flowchart illustrating a method for constructing CFRPpanels in an example embodiment.

DETAILED DESCRIPTION

The figures and the following description illustrate specific exemplaryembodiments. It will be appreciated that those skilled in the art willbe able to devise various arrangements that, although not explicitlydescribed or shown herein, embody the principles described herein andare included within the contemplated scope of the claims that followthis description. Furthermore, any examples described herein areintended to aid in understanding the principles of the disclosure, andare to be construed as being without limitation. As a result, thisdisclosure is not limited to the specific embodiments or examplesdescribed below, but by the claims and their equivalents.

FIG. 1 illustrates an aircraft 100 in an example embodiment. Theaircraft 100 includes nose 110, wing 120, fuselage 130, and tail 140.Further discussion of the aircraft 100 focuses on composite material ofthe wing 120 of the aircraft 100. However, similar configurations andtechniques to those described herein may be applied to any suitablecomposite part for the aircraft 100 as well as alternative aircrafts andother types of vehicles.

FIG. 2 illustrates the wing 120 of the aircraft 100 that includes acomposite structure 210 of multiple Carbon Fiber Reinforced Plastic(CFRP) panels 220 in an example embodiment. In particular, the compositestructure 210 comprises a portion of an upper wing skin. The view ofFIG. 2 is shown by view arrows A of FIG. 1 . As shown in FIG. 2 , eachCFRP panel 220 comprises a small portion of the area of the compositestructure 210. View arrows B along FIG. 2 indicate a possible view alongthe length of the wing 120.

FIG. 3 is a partially exploded view 300 of the CFRP panels 220 joinedtogether by a fastener 310 in an example embodiment. In this view, theCFRP panels 220 are shown separated to illustrate the joinedconfiguration of the CFRP panels 220, which may be in contact despitetheir apparent separation in this exploded view. Particularly, oppositeends of a first CFRP panel 220-1 and a second CFRP panel 220-2 overlapvertically (i.e., in the z-direction) to form respective overlap areas311-312 (i.e., in the xy-plane) defined by boundaries 321-322. The CFRPpanels 220 each include one or more layers 330 of carbonfiber-reinforced plies. The fibers may have different orientations amongthe layers 330 to increase strength of the CFRP panels 220 alongdifferent dimensions.

The fastener 310 is inserted through the CFRP panels 220 in the verticaldirection (i.e., z-direction) to join the CFRP panels 220 together. Theterm vertical direction denotes a relative position of the CFRP panels220 that is generally parallel with a thickness of the CFRP panels 220and perpendicular to a flat plane of the CFRP panels 220, althoughalternative geometries of the CFRP panels 220 other than that shown inFIG. 3 is possible. In general, the fastener 310 includes a conductivemetallic material (e.g., aluminum, titanium, stainless steel, etc.) andmay include a bolt and a nut, a rivet, a blind fastener, or anotherfastener device suitable for mechanically joining the CFRP panels 220.As such, the fastener 310 provides a through-thickness conductivity inthe CFRP panels 220 in the z-direction, sometimes referred to herein asa vertical direction. The layers 330 of the CFRP panels 220, bycontrast, have anisotropic conductivity in which current is forced in adirection parallel along the layers 330 in the xy-plane. As a result,when lightning strikes one of the CFRP panels 220, high levels ofcurrent may be undesirably concentrated at the fastener 310, potentiallydegrading the integrity of the fastening connection or causing thefastener 310 to spark and create an ignition hazard.

FIG. 4 illustrates a partially exploded view 400 of the CFRP panels 220joined together by a fastener 310 and enhanced with electricallyconductive pins 450 in an example embodiment. The pins 450 may includeany suitable material (e.g., carbon, aluminum, titanium, etc.) having along axis extending generally in a vertical direction (i.e.,z-direction) to electrically connect the CFRP panels 220. The pins 450generally differ from the fastener 310 in terms of size, numbers, andfunction. For example, multiple pins 450 may surround a single fastener310 in the xy-plane and individually occupy a fraction of the area inthe xy-plane as compared to the fastener 310 (e.g., so as not to degradethe structural integrity of the CFRP panels 220). In other embodiments,the pins 450 may surround multiple fasteners 310. In furtherembodiments, the pins 450 may provide paths for electrical currentwithout any mechanical fastening means. In general, the pins 450 aredistributed/interspersed throughout the overlap areas 311-312 of theCFRP panels 220 to provide a technical benefit of spreadingthrough-thickness current conduction away from the fastener 310 todecrease current concentration at the fastener 310 and thus decrease theprobability of current-induced damage at or near CFRP-fastenerinterfaces.

FIG. 5 is a side view 500 of the CFRP panels 220 joined together by afastener 310 and enhanced with electrically conductive pins 531-532 inan example embodiment. As illustrated by this example, the first CFRPpanel 220-1 includes a top surface 510, a bottom surface 511, and afirst group of pins 531. Similarly, the second CFRP panel 220-2 includesa top surface 512, a bottom surface 513, and a second group of pins 532.Thus, each of the CFRP panels 220 may include its own subset of the pins531-532. For example, the first group of pins 531 may be inserted into awet layup of the first CFRP panel 220-1 prior to cure, the second groupof pins 532 may be inserted into a wet layup of the second CFRP panel220-2 prior to cure, and the pins 531-532 may be cured with theirrespective CFRP panels 220.

In general, when the CFRP panels 220 are properly fastened together withthe fastener 310, a portion of the bottom surface 511 of the first CFRPpanel 220-1 contacts a portion of the top surface 512 of the second CFRPpanel 220-2. That is, although FIGS. 3-9 show gaps between the CFRPpanels 220 to more clearly illustrate placement of the pins 531-532, theCFRP panels 220 are pressed against each other when the fastener 310 isattached. The vertically stacked, horizontally offset configuration ofthe CFRP panels 220 creates an overlap area 520 defined by the opposingfar ends 521-522 of the CFRP panels 220, as illustrated by the dashedlines in FIG. 5 . The overlap area 520 is similar to the overlaps areas311-312 described above in FIGS. 3-4 and is generally an area in thexy-plane that is defined by the vertical overlapping of the CFRP panels220 in the z-direction. As such, the overlap area 520 may vary accordingto size, shape, and installation configuration of the CFRP panels 220.

As further illustrated in this example, the first group of pins 531 inthe first CFRP panel 220-1 have a first spacing 561 (e.g., in thexy-plane) between one another in the overlap area 520, and the secondgroup of pins 532 in the second CFRP panel 220-2 have a second spacing562 (e.g., in the xy-plane) between one another in the overlap area 520.The first spacing 561 and the second spacing 562 may have acorresponding configuration or pattern such that at least a subset orportion of the total number of the first group of pins 531 contacts atleast a subset or portion of the total number of the second group ofpins 532 when the CFRP panels 220 are properly joined. That is, thefirst spacing 561 and the second spacing 562 may correspond to ensuresufficient electrical contact between the CFRP panels 220 and sufficientcurrent paths in the z-direction away from the fastener 310 yet withinthe overlap area 520 that effectively decreases damage from a lightningstrike.

In one embodiment, the pins 531-532 may be installed in the CFRP panels220 according to a semi-random pattern to achieve a desired effectivedensity. For example, while individual pins 531-532 may be located alongthe xy-plane randomly, the density of the pins 531-532 per unit area inthe overlap area 520 may remain uniform or constant. Thus, the CFRPpanels 220 enhanced with the pins 531-532 may be manufactured to ensurethat a predefined minimum amount of electrical contact is to be madewhen joined/fastened with another one of the CFRP panels 220.

The pins 531-532 may also have various lengths and configurations in thez-direction of the CFRP panels 220. As illustrated in FIG. 5 , the pins531-532 may traverse the entire thickness of the CFRP panels 220 toelectrically connect the layers 330 (not shown in FIG. 5 for ease ofillustration) from a top surface 510/512 to a bottom surface 511/513 ofthe CFRP panels 220. Alternatively or additionally, the pins 531-532 maytraverse a portion of the thickness of the CFRP panels 220 toelectrically connect a portion of the layers 330 of the CFRP panels 220.Thus, the CFRP panels 220 enhanced with the pins 531-532 provides atechnical benefit to reduce ply-to-ply energy transitions between thelayers 330 (e.g., due to differences in fiber orientations and theanisotropic conductivity of the layers 330) and thus reduce thepotential for edge glow or particle ejection as a result of a lightningstrike at or near the CFRP panels 220.

Moreover, the pins 531-532 may be exposed at, or protrude from, the topsurface 510/512 and/or bottom surface 511/513 of the CFRP panels 220 ina variety of configurations. The pattern of exposure of the pins 531-532at the top surface 510/512 and/or bottom surface 511/513 may correspondamong the CFRP panels 220 to ensure a desirable level of electricalcontact in the overlap area 520, similar to that as already describedabove with respect to the first spacing 561 and the second spacing 562of the pins 531-532. Furthermore, in some embodiments, the pins 531-532may be parallel with the fastener 310 and/or perpendicular to the topsurface 510/512 and/or bottom surface 511/513 of the CFRP panels 220(e.g., parallel with the z-direction). It will be appreciated, however,that numerous configurations of the pins 531-532 are possible, examplesof which are further described below.

FIG. 6 is a side view 600 of the CFRP panels 220 enhanced withelectrically conductive pins 531-532 in another example embodiment. Asshown in this example, each of the pins 531-532 may include a shank 630and a head 640. The shank 630 is generally an elongated membertraversing a thickness of one of the CFRP panels 220. The head 640 isaffixed to a far end of the shank 630 and is exposed or protrudes thetop surface 510/512 and/or a bottom surface 511/513 of one of the CFRPpanels 220. As such, the pins 531-532 of the CFRP panels 220 maycorrespond according to patterns, spacing, and/or sizes of the heads 640exposed at the top surface 510/512 and/or a bottom surface 511/513 ofone of the CFRP panels 220 such that the heads 640 contact each otherwhen the CFRP panels 220 are properly fastened. Alternatively oradditionally, the pins 531-532 may be configured such that at least someportion of the pins 531-532 are not in direct contact but are withinsufficient proximity to the pins 531-532 of another CFRP panel toelectrically connect the two CFRP panels 220.

FIG. 7 is a side view 700 of the CFRP panels 220 enhanced withelectrically conductive pins 730 in yet another example embodiment. Asshown this example, the pins 730 may be inserted into the first CFRPpanel 220-1 and the second CFRP panel 220-2 by puncturing through athickness of the first CFRP panel 220-1 and the second CFRP panel 220-2.That is, the pins 730 may be installed into the CFRP panels 220 afterthe CFRP panels 220 are cured and/or joined together by the fastener310. As illustrated in FIG. 7 , the pins 730 may be inserted lengthwiseinto the CFRP panels 220 to electrically connect between various endpoints along the z-direction. Such a configuration may advantageouslydistribute current among various layers 330 (not shown in FIG. 7 forease of illustration) to spread current from a lightning strike andreduce potential damage resulting therefrom. Features, possibleconfigurations, and advantages of the pins 730 are similar to thatalready described above with respect to the pins 450 and 531-532 andthus description of such is omitted for sake of brevity.

FIG. 8 is a side view 800 of an adjacent CFRP panel 220-3 connected withelectrically conductive pins 830 in an example embodiment. As shown inthis example, the first CFRP panel 220-1 and the adjacent CFRP panel220-3 may contact/align horizontally. The first CFRP panel 220-1 and theadjacent CFRP panel 220-3 may also be joined to a common CFRP panel(e.g., the second CFRP panel 220-2) via fasteners 310. The pins 830 maybe punctured into the CFRP panels 220 to electrically connect the firstCFRP panel 220-1 and the adjacent CFRP panel 220-3. The pins 830 aregenerally oriented lengthwise along the xy-plane, but may have endpoints at different locations along the z-direction to spread current tovarious layers 330 (not shown in FIG. 8 for ease of illustration) of theCFRP panels 220.

FIG. 9 is a side view 900 of adjacent CFRP panels 220 connected withelectrically conductive pins 830 in another example embodiment. As shownin this example, the first CFRP panel 220-1 and the second CFRP panel220-2 may contact/align horizontally. Moreover, the first CFRP panel220-1 and the second CFRP panel 220-2 may each include a metal foil910/912 or mesh along respective top surfaces 510/512. The metal foil910/912 may include, for example, a copper or aluminum skin of theaircraft 100. The first CFRP panel 220-1 and the second CFRP panel 220-2further include a first group of pins 931 and a second group of pins932, respectively. The pins 931-932 extend in the z-direction into themetal foil 910 at one end and may protrude at the bottom surfaces511/513 of the CFRP panels 220 at the other end.

The fasteners 310 join the CFRP panels 220 to a metallic frame 950. Themetallic frame 950 may include, for example, a structural body of theaircraft 100 (e.g., aluminum, titanium, etc.) such as a frame, rib,stringer, etc. As the fasteners 310 are tightened, the metallic frame950 may be pressed into the protruding ends of the pins 931-932 toelectrically connect the first CFRP panel 220-1, the second CFRP panel220-2, and the metallic frame 950. In some embodiments, the pinsdescribed herein may be located within proximity of the fasteners 310 tosufficiently spread currents along different paths in the z-directionfor a particular area (e.g., similar to the overlap areas describedabove). Alternatively or additionally, one or more of the pins describedherein may be located outside such a particular area to distributecurrents in areas other than fastener-CFRP interfaces.

FIG. 10 is a block diagram of a composite manufacturing environment 1000in an exemplary embodiment. According to FIG. 10 , the environment 1000includes a composite design system 1010, which is capable of designingCFRP panels 220. Composite design system 1010 configures CFRP panels 220to a desired strength and conductivity at or near CFRP-fastenerinterfaces and may direct the Automated Fiber Placement (AFP) machine1040 to manufacture CFRP panels 220 according to the design.

The composite design system 1010 includes controller 1012, interface(I/F) 1014, and memory 1016. Controller 1012 utilizes I/F 1014 to accessrules constraining how CFRP panels 220 may be constructed, informationdescribing the geometry of CFRP panels 220, and/or other information.The I/F 1014 may acquire this information from server 1030 via a network1020. Controller 1012 also generates designs for CFRP panels 220 whichmay be stored by controller 1012 within memory 1016. Controller 1012 maybe implemented, for example, as custom circuitry, as a processorexecuting programmed instructions, or some combination thereof. I/F 1014comprises any suitable combination of circuitry and/or components fortransmitting data (e.g., via network 1020). Memory 1016 comprises anysuitable data storage device such as a hard disk, flash memory, etc.Further details of the operation of composite design system 1010 will bedescribed with regard to FIG. 11 below.

FIG. 11 is a flowchart illustrating a method 1100 for constructing CFRPpanels 220 in an example embodiment. The steps of method 1100 aredescribed with reference to composite design system 1010 of FIG. 1 , butthose skilled in the art will appreciate that method 1100 may beperformed in other systems. The steps of the flowcharts described hereinare not all inclusive and may include other steps not shown. The stepsdescribed herein may also be performed in an alternative order.

In step 1102, the controller 1012 identifies a first CFRP panel and asecond CFRP panel to be joined. In doing so, the controller 1012 mayreceive input via the I/F 1014 indicating a geometry of one or more ofthe CFRP panels 220. This information may indicate which CFRP panels areadjacent/neighboring, and may further include an expected number ofplies for each different fiber orientation to be laid at each CFRP panel(e.g., a final depth/thickness and composition).

In step 1104, the controller 1012 determines an area where the firstCFRP panel and the second CFRP panel overlap in the vertical direction.In step 1106, the controller 1012 determines a location for a fastenerto be inserted into the area to join the first CFRP panel and the secondCFRP panel. In step 1108, the controller 1012 directs the AFP machine1040 to insert a plurality of electrically conductive pins into the areain the vertical direction at positions proximate to the location for thefastener. The area may be the overlap area of the panels previouslydescribed.

The pins may be inserted/punctured into an already cured CFRP panel orinserted/positioned in a wet lay-up of the CFRP panel and then curedwith the CFRP panel. For instance, the CFRP panels may include layers330 bonded together by a polymer matrix material (e.g., a thermosetresin such as epoxy or a thermoplastic) consecutively laid up and curedto form the CFRP panel, referred to as wet lay-up. The AFP machine 1040may position the pins in the wet lay-up at locations around where thefastener is to be located and in various patterns across the overlaparea as previously described. The particular number and/or location ofthe pins inserted into the CFRP panel may be defined according to designconsiderations that balance strength of the CFRP panel at theoverlapping area with the desired spread of conductivity in theoverlapping area that provide current paths in the z-directionalternative to that provided by the fastener. In some embodiments,multiple CFRP panels or parts may be co-cured, meaning they are laid upand then cured together.

The method 1100 of FIG. 11 may advantageously provide the improvedelectrical conductive feature of the panels described above in anautomated fashion and without any additional cure time. Previoustechniques for lightning mitigation include secondary operations (e.g.,covering the fastener with a polysulfide cap seal, applying edgesealant, and/or bonding existing panels with a conductive splice) whichincrease the cost and flow time of aircraft production and alsoundesirably increase the parasitic weight of the aircraft. By contrast,the configuration and techniques of inserting the pins as describedherein accomplish more evenly distributed current densities in the CFRPstructures in a manner that minimizes impact on factory flow time andaircraft weight.

Any of the various elements shown in the figures or described herein maybe implemented as hardware, software, firmware, or some combination ofthese. For example, an element may be implemented as dedicated hardware.Dedicated hardware elements may be referred to as “processors”,“controllers”, or some similar terminology. When provided by aprocessor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, a network processor, application specific integrated circuit(ASIC) or other circuitry, field programmable gate array (FPGA), readonly memory (ROM) for storing software, random access memory (RAM),non-volatile storage, logic, or some other physical hardware componentor module.

Also, an element may be implemented as instructions executable by aprocessor or a computer to perform the functions of the element. Someexamples of instructions are software, program code, and firmware. Theinstructions are operational when executed by the processor to directthe processor to perform the functions of the element. The instructionsmay be stored on storage devices that are readable by the processor.Some examples of the storage devices are digital or solid-statememories, magnetic storage media such as a magnetic disks and magnetictapes, hard drives, or optically readable digital data storage media.

Although specific embodiments were described herein, the scope is notlimited to those specific embodiments. Rather, the scope is defined bythe following claims and any equivalents thereof

What is claimed is:
 1. A composite structure for an aircraft, thecomposite structure comprising: a plurality of Carbon Fiber ReinforcedPlastic (CFRP) panels that are horizontally adjacent with one another,each CFRP panel including: an upper surface having a mesh foil; afastener inserted through the CFRP panel in a vertical direction, thefastener configured to secure the CFRP panel to a metallic frame of theaircraft located proximate to a lower surface of the CFRP panel; and aplurality of electrically conductive pins extending in the verticaldirection to electrically connect the mesh foil and the metallic frameof the aircraft.
 2. The composite structure of claim 1, wherein: thepins are configured to extend beyond the lower surface of the CFRP panelprior to tightening the fastener and do not contact the metallic frameof the aircraft prior to tightening the fastener; and the pins areconfigured to contact the metallic frame of the aircraft aftertightening the fastener.
 3. The composite structure of claim 1, wherein:the pins are configured to puncture the CFRP panels.
 4. The compositestructure of claim 1, wherein: the composite structure comprises a wingof the aircraft.
 5. The composite structure of claim 1, wherein: thepins are parallel with the fastener and perpendicular to compositelayers of each of the CFRP panels.
 6. The composite structure of claim1, further comprising: another plurality of electrically conductive pinsextending horizontally in a direction perpendicular to the verticaldirection to electrically connect adjacent ones of the CFRP panels. 7.The composite structure of claim 1, wherein: the fastener is configuredto mechanically join a CFRP panel with the metallic frame, the pinsextend through the CFRP panel to provide a path for electrical currentaway from the fastener, and the pins include a longitudinal body thatdoes not mechanically join the CFRP panel with the metallic frame. 8.The composite structure of claim 1, wherein: the pins are distributedwithin an area of a CFRP panel to spread through-thickness currentconduction away from the fastener.
 9. The composite structure of claim1, wherein: each of the pins is individually smaller than the fastener.10. The composite structure of claim 1, wherein: a material of the pinsincludes one of carbon, aluminum, and titanium.
 11. The compositestructure of claim 1, wherein: one of the CFRP panels is directly incontact with another of the CFRP panels.
 12. The composite structure ofclaim 1 wherein: each of the pins is distinct from others of the pins.13. The composite structure of claim 1 wherein: a diameter of each ofthe pins is less than a diameter of the fastener.
 14. The compositestructure of claim 1 wherein: the CFRP panels are co-cured with thepins.
 15. The composite structure of claim 1 wherein: layers of the CFRPpanels exhibit anisotropic conductivity.
 16. The composite structure ofclaim 1 wherein: multiple ones of the pins surround a single fastener.17. A composite structure for an aircraft, the composite structurecomprising: a plurality of Carbon Fiber Reinforced Plastic (CFRP) panelsthat are horizontally adjacent with one another, wherein neighboringCFRP panels are in direct contact with each other, each CFRP panelincluding: an upper surface having a mesh foil; a fastener insertedthrough the CFRP panel in a vertical direction, the fastener configuredto secure the CFRP panel to a metallic frame of the aircraft, locatedproximate to a lower surface of the CFRP panel; and a plurality ofdistinct electrically conductive pins extending in the verticaldirection to electrically connect the mesh foil and the metallic frameof the aircraft, wherein a diameter of each of the pins is less than adiameter of the fastener.
 18. A composite structure for an aircraft, thecomposite structure comprising: a plurality of composite panels thatform a wing of the aircraft, wherein the composite panels arehorizontally adjacent with one another, each composite panel including:an upper surface having a metal mesh; a fastener inserted through thecomposite panel in a vertical direction, the fastener configured tosecure the composite panel to a frame of the aircraft located proximateto a lower surface of the composite panel; and a plurality ofelectrically conductive pins extending in the vertical direction toelectrically connect the upper surface of the composite panel and theframe of the aircraft.
 19. The composite structure of claim 18, wherein:the pins are parallel with the fastener and perpendicular to compositelayers of each of the composite panels.
 20. The composite structure ofclaim 18, further comprising: another plurality of electricallyconductive pins extending horizontally in a direction perpendicular tothe vertical direction to electrically connect adjacent ones of thecomposite panels.